Renal transplant and secondary hyperparathyroidism

Abstract

To investigate the impact of mineral metabolism, renal function, months on dialysis and months since transplant for predicting intact parathyroid hormone (iPTH) levels in a cohort of patients who had undergone their first renal graft with estimated glomerular filtration rates (eGFRs) of 30-60 and >60 ml/min/1.73 m2. One hundred and twenty-eight patients (mean age 56.0 +/- 14.6 years) with an eGFR of >30 ml/min/1.73 m2 were included. The median time since transplant was 88.6 months (range 2.8-403.2 months). Blood samples were collected for measurement of iPTH, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, calcium, albumin, phosphate and creatinine. The eGFR was calculated using the formula for the modification of diet in renal disease. One hundred and three patients (80%) had an elevated level of iPTH, 29 (23%) had hypercalcaemia and 42 (35%) had a 25-hydroxyvitamin D3 level of <40 nmol/L. In stepwise backward regression, eGFR and 25-hydroxyvitamin D3 were associated with iPTH, as follows: iPTH = 24.91 -(0.06 x 25-hydroxyvitamin D3) - (0.16 x eGFR) (R2 = 0.14). No associations with these two variables were, however, detected in patients with an eGFR of >60 ml/min/1.73 m2. Forty patients (31%) were transplanted pre-emptively, and the iPTH concentrations were significantly lower in these patients. Decreasing eGFR was the single most important variable predicting iPTH level in a cohort of renal transplant patients with an eGFR of 30-60 ml/min/1.73 m2, but not in patients with an eGFR of >60 ml/min/1.73 m2. Patients transplanted pre-emptively had a statistically significantly lower iPTH level compared with patients who had received dialysis.